Electrum wallet is not designed for this. in general, as long as your computer is running, your Electrum wallet can scan any number of addresses, but since it is an SPV wallet[1], most Electrum servers have a DoS-protection limit, which is often less than ~10k addresses[2], so if you have a number greater than 10k, the electrum option will be slow and time-consuming (and here we are talking about 86k, not 10k).
You can avoid this by running full node, so bitcoin core is the appropriate choice.
Running a Bitcoin Core full node is a best option but it is best if this balance checking activity needs to repeat many times, like daily check.
If it is only one time check with curiosity only, I don't see why we need to run a full node. The OP's purpose is not to check these addresses' balance too often, it's my guess. Depends on the purpose, Electrum or Bitcoin Core full node can be used.
With 86k private keys ~ addresses, we can split it to 9 parts and check each of 9 parts. Do you think it can avoid Dos-protection and won't be too slow and time-consuming?